JPH02270905A - Compression of metal web - Google Patents

Abstract

PURPOSE: To manufacture a non-woven metal web suitable for a filter and a radiant surface combustion burner by supporting the one side surface of the non-woven metal web with a steel plate, etc., pressing and compressing the other surface with oil medium through a soft isolating plate and making a compact body roughened surface in the one side surface. CONSTITUTION: At the time of manufacturing the non-woven metal web having extremely fine metallic fibers, the one side surface in two non-woven metal webs 1 are abutted on the stainless steel plate 2 and supported, and the flexible isolating plates 3 such as plastic foil and rubber foil, are set on the other surface and compressed by pressing P with an oil medium 4 through the soft isolating plate 3. As the other way, the non-woven web 1 is supported on the supporting plate 2 such as the stainless steel plate and compressed with a compressing plate 6 through a thin felt member 5 laid on the upper surface. In this case, the non-woven fired metal web suitable for the filter, etc. having <=10% variation of permeability shown with the equation, is obtd. by isotropically cold- compressing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of compacting a nonwoven fired metal web. Also,
The present invention relates to a nonwoven fired metal web obtained by the method described above. Such nonwoven metal webs are used in filters and radiant burners.
5 surface combuLlon burner)
It can be used for.

A nonwoven metal web is defined as having a diameter of less than 100 μm, preferably less than 60 μm (e.g. 25 μm 1
A web made of metal fibers having a diameter of 15 μm, 2 μm, 1.5 μm, etc.). These metal fibers have a rough outer surface and are randomly distributed throughout the web. And, due to the frictional action of the rough surface, they are entangled in a substantially singly mixed relationship. Nonwoven metal webs consist of two or more layers, each layer consisting of metal fibers of approximately the same diameter. However, the diameters of the metal fibers constituting different layers do not have to be equal to each other.

Note that nonwoven metal web also refers to a nonwoven metal web reinforced with one or more wire meshes.

The non-woven metal web is manufactured by British Patent Box 1.190°844 (
GBl, 190.844)
Feeder Unibar 1t (rando-1'eder
-vebber apparatus).

The nonwoven metal web may be sintered or unsintered, but sintered bodies are preferred in the context of the present invention. This is because sintering forms bonds at the points where different fibers intersect.

It is known to use nonwoven metal webs in filters. One of the important characteristics of a filter is the pore size (p
ore5ize). This is because pore size can determine the size of particles captured by the filter. Traditionally, nonwoven metal webs have been compacted by compression or rolling to obtain specially defined pore sizes.

However, these conventional compressed nonwoven metal webs have
There were certain limits. For example, the density (i.e., compactness) that corresponds to a particular pore size
; see below for exact definition) is a fairly high value. As a result, filters have relatively high pressure drops, requiring the use of large filter surfaces or the use of ventors or high-power pumps.

On the other hand, it is also known to use nonwoven metal webs as panels in radiant surface combustion burners. These burners are capable of true radiant surface combustion. That is, these burners emit a blue flame (blue['lag+e) or a free flame (fr
There is no ee r 1aIle). However, conventionally,
True radiant surface combustion was only possible using nonwoven metal webs with a critical area of less than about 40.000 mm 2 (and this is not constant). Or, if you want to use an area larger than 4.0.00C)u*2, 500kv/rr? or had to be done with less heat output. This represents a severe limitation in its application to the burner.

The present invention has been made in view of the above-mentioned matters, and an object of the present invention is to reduce the limitations imposed by the conventional technology. Also,
The present invention aims to provide a method for compressing a nonwoven fired metal web and to provide a nonwoven metal web produced by said method and which can be adapted for use in filters. Furthermore, the present invention also aims to provide a nonwoven metal web produced by the method and applicable for use in radiant surface combustion burners.

According to a first aspect of the present invention, there is provided a method for compressing a non-woven metal web (preferably a non-woven fired metal web), the method comprising compressing a non-woven metal web or the like into an isostatically compressed wire (preferably a cold isostatically compressed web). ) is provided.

Isostatic pressure means that the pressure is transmitted by the medium such that the pressure is equal at each point on the surface of the material to be treated (in the present case, the nonwoven metal web).

The medium can be a gas, a liquid, a felt-like material, a soft septum or a combination of a soft septum and a gas or a liquid. When the applied pressure is high (greater than 1000 bar) and the surface area of the treated material is small (250, OO'O Long 2
(smaller), an oil medium is suitable. When the applied pressure is less than the previous pressure or when the previous surface area is larger, it is more preferable to use a combination of oil and rubber or a felt-like material as the medium.

Cold isostatic pressing means that the entire process is carried out at room temperature.

"Isostatically compressing such a nonwoven metal web" means compressing the nonwoven metal web isotropically, except for the separator between the web and the compression medium, and possibly the substrate. means to be

The immediate effect of isostatic pressing is that conventional compaction by compaction plates or rolls is no longer necessary.

In many cases, the effects before isostatic pressure can be easily seen on the product. For example, a nonwoven fired metal web compressed by conventional rolls or compression plates has two flat outer surfaces. However, an isobarically compressed nonwoven fired metal web, on the other hand, does not have two perfectly flat surfaces.

at least one surface has a small thickness variation;
As a result, the surface has a rough and dull appearance.

According to a second aspect of the invention, a nonwoven metal web (preferably a nonwoven fired metal web) is provided.

Such a nonwoven metal web can be a nonwoven metal web adapted for use in filters. Nonwoven metal webs adapted for use in filters have a diameter of less than 50 μm, preferably a diameter of less than 251 t m (e.g.
6.5 μm or 2.0 μm), etc.

Such nonwoven metal webs may also be used in radiant surface combustion burners. The non-woven metal web adapted for use in radiant surface combustion burners is made of metal fibers having a diameter of less than 100 μm, preferably less than 60 μm and containing chromium, aluminum and yttrium, titanium or niobium as stable elements. Become. Examples of suitable alloys are FeCrAIY, FeCrAlNb.

There are FeN1CrAIY and FeNiCrAlNb.

Non-woven metal P, □, applicable for use in radiant surface combustion burners
- P wal n.

The genus web has transparency changes , , , , x i
o.

is preferably less than 10%.

Mizuhiki! The reason why permeability variation is used in place of the commonly used M1-logical return δ in the II book is that the flame of a radiant surface burner emerges in the most permeable region of the nonwoven metal web. . Only the part that is more permeable is important for creating the blue flame patch. As a result, the extreme value (extr
eme value ) is a value suitable for checking the condition of the radiant surface combustion burner.

The transmittance P is rn3/h, m2. It is expressed as

This transmittance P can be measured by the following method.

The nonwoven metal is divided into equal squares, each with a surface of 2500 mm2. To examine the permeability of each square, two semi-cylinders each with an internal diameter of 35 mm are placed in a straight line on each side of the nonwoven metal web. 1000 Pascals (Pa) on the other side of the nonwoven metal web
Apply a pressure drop of and measure the air flow rate. Dividing this flow rate by the cross-sectional area gives the permeability P.

P□8. is the maximum fluid permeability determined by lpI at any point along the web surface, P16. is the minimum value of fluid permeability measured at any point along the web surface.

The reasons why the method of the present invention alleviates the limitations of the prior art will be explained below.

For example, non-woven metal webs such as those produced by the land feeder Univer apparatus (GB 1.190.844) are not very homogeneous (and therefore undesirable for use in filters and radiant surface combustion burners). The weight change per unit surface is too large.On the contrary, even with sintering and/or compaction by conventional compaction or rolling,
The homogeneity of the nonwoven metal web is not improved.

The inventors have found that isotropic compression improves the homogeneity of nonwoven metal webs as an alternative to traditional compression methods. Furthermore, this improved homogeneity results in better properties of the nonwoven metal web (small pore size and low pressure drop) when used as a filter, and when used in radiant surface combustion burners. It has been found that better properties of the nonwoven metal web (smaller change in permeability) can be obtained.

The present invention can be fully understood by reference to the following description and accompanying drawings.

FIGS. 1 and 2 are diagrams schematically showing the principle of isotropically compressing the nonwoven metal web 1. FIG. According to FIG. 1, pressure is applied to one side of the nonwoven metal web. Therefore, after this compression process, the web 1 has one rough surface. According to FIG. 2, pressure is applied from both sides of the web, and after this compression process, the web 1 has two rough surfaces (in FIGS. 1 and 2,
roughness is emphasized).

FIG. 3 shows the arrangement in an oil medium. According to this, two nonwoven metal webs 1 are supported by a stainless steel plate 2. Two soft separators 3 are arranged between the two metal webs 1 and the oil medium 4 to prevent the webs 1 from becoming contaminated with oil. This soft separator has
Plastic or rubber foils are suitable.

In FIG. 4, the pressure medium is a thin felt-like material 5. In FIG.

The web 1 is arranged between the felt-like material 5 and the support 2. A conventional compression plate 6 can also be used for compression.

Isostatic compression, particularly cold isostatic compression, is widely known in the art. Examples of earlier patents in this field include U.S. Patent No. 1,018,618; U.S. Patent No. 1,863;
, 854 and U.S. Pat. No. 1,864.365.

The advantageous effects of applying isotropic compression in filter applications can be easily understood from FIGS. 5-7.

FIG. 5 shows the relationship between absolute pore size a and density δ. The absolute size a is determined by the extended bubble point pressure test (extended bubble point pressure test).
The meaning is the same as the mean flow pore size measured by pressure test). This test is
It can be carried out continuously with a Coulter bolometer controlled by a microprocessor. A more detailed description of this test method can be found in R. De Br.
Uync) in the following document.

“Application of “non-media” standards in the design and testing of filter media, R&D innovations in filtration”: 12 best papers of the 10th anniversary contest organized by the Belgian Filtration Association Pages 75-108 Density δ (0≦δ≦ 1) is the ratio of the amount of nonwoven metal web to a block having the same volume as the nonwoven metal web and made of the same metal. The porosity value ε corresponds to the density 1−δ. Density δ and porosity can be expressed as a percentage (%).

Curve 7 in FIG. 5 represents the ideal relationship between pore size a and density δ. That is, curve 7 represents the relationship when the web is completely homogeneous. The shaded area 8 corresponds to the value obtained by isotropic compression. Moreover, the shaded area 9 corresponds to the value obtained by conventional compression.

Specific example: Beklpor 3A
12 web is used. This web consists of four layers, gi
A stainless steel web with a Q of about 850 to 950 g/rd. To obtain an average flow pore size a of 1 μm, the nonwoven fired metal web must be isotropically compressed until the density δ is approximately 50%. That is, it must be compacted to a porosity ε of approximately 50%.

With conventional compression methods, the nonwoven fired metal web must be compressed to a density δ of 70% (i.e., a porosity ε of 30%) to obtain the same average flow pore size of 1 μm as described above. . This means that for the same pore size, an isotropically compressed web is more porous than a conventionally compressed web. Also,
Comparing the same porosity ε means that an isotropically compressed web can have smaller pore sizes than a web compressed by conventional methods.

This is quite important. Figure 6 is a diagram showing the relationship between ε・a, which is the porosity multiplied by the pore size, and the permeability coefficient 1 (different from the permeability P). do not have).

It has been experimentally found that this relationship can be expressed by the following formula.

k-0,033
The permeability coefficient obtained by isobaric compression is three times the permeability coefficient obtained by conventional compression methods.The following Darcy equation (where ΔP is pressure drop, Q is flow rate, H is filter thickness, A is filter area, μ
is the viscosity coefficient and k is the permeability coefficient), this means that the pressure drop in the web of the present invention is three times lower than that in a conventionally compressed web. This lower pressure drop allows the use of smaller surfaces or lower powered pumps or vents.

On the other hand, FIG. 7 shows other advantages. Figure 7 shows the foreign matter holding capacity F (formerly rt holding capaclt).
y ) to the transmission coefficient and 1. (The scale in Figure 7 is not an equal division scale.) It was experimentally found that this relationship can be expressed by the following formula.

F-3,48'°30 Foreign material retention volume uF is the amount of artificial foreign material that can be added to the filter element before the pressure drop at constant flow rate becomes unacceptably high. In a specific example, the F value of the web of the present invention is 16.0+ng/c, while the F value of the web with conventional compression is 11.5 mg/c.

This means that the invention reduces the number of web jams and reduces production losses due to jams.

Test Example 1 Table 1 summarizes the results of an isostatic line test applied to a nonwoven metal web (trade name: Bekipor 3^12) adapted for use in filters. The compression medium is oil. In Test Examples 1 to 4, the web was sintered before isotropically compressed; in Test Examples 5 and 6, it was not sintered. Pore sizes a and δ(a) are determined by extensive bubble point testing.

In order to obtain a copy of the specification (no changes to the content), the pressure applied with isostatic compression must be between 3000 and 3500 bar.

Test Example 2 The second test compares an uncompressed fired 3A12 web to an isotropically compressed fired 3A12 web.

In the same way as above, to find the two values, the transparency P
was measured, but instead of applying 1000 pascals, 2
A pressure drop of 0.00 Pascals was applied. The compression medium is a combination of rubber septum and oil.

The results of this test example are summarized in Table 2.

Table 2 Isotropic compression test using a combination of rubber and ura as a medium Table 2 shows that isotropic compression significantly reduces the change in transmittance P.

Test Example 3 Four conventionally compressed fired PeCrAIY webs were compared with four isotropically compressed fired PcCrAIY webs. The applied isostatic pressure p is 50 bar. The pressure drop across the web was 1000 Pascals. The results of this test example are summarized in Table 3.

Reprint of the specification (no changes to content) To evaluate these results, we applied the following rules of thumb.

Before the appearance of the first blue flame zone, i.e. before the nitrogen oxide exceeds 100 ppm, a transmission of 5% kW/d
Corresponding to
Corresponding to rr, a 20% change in transmittance results in a heat output of 500kW
Corresponds to /rd. This means that the web of the present invention can tolerate greater heat output due to true radiant surface combustion.

The invention is not limited to any particular filter application. Isotropically compressed webs can be used for filter gases, fuels, polymers, and other liquids. Furthermore, the present invention provides ii? 1μm determined by I
The pore size is not limited to a. The present invention
Pore size smaller than 0.5 μm (e.g. 0.4 μm
or 0.3 μm) can be used to obtain nonwoven metal webs adapted for use in filters.

Also, the invention is not limited to the geometry of the fired web. Isobaric compression can be applied to flat nonwoven fired metal webs as well as cylindrical shaped webs.

Isobaric compression can be applied not only to nonwoven metal webs, but also to bonded glass fibers and metal foams.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of isobaric compression. FIG. 2 is a diagram showing the principle of isobaric compression. FIG. 3 is a diagram showing the arrangement in an oil medium. FIG. 4 is a diagram showing a case where a felt-like material is used as the compression medium. FIG. 5 is a diagram showing the relationship between the pore size a and the density δ for a specific fiber diameter. Figure 6 shows ε・a, which is the porosity ε multiplied by the pore size a, and
A diagram showing the relationship between the transmission coefficient and the transmission coefficient. FIG. 7 is a diagram showing the relationship between foreign matter holding capacity F and transmission coefficient. 1... Nonwoven metal web, 2... Stainless steel plate, 3
... Soft separator, 4... Oil medium, 5... Felt-like material Applicant's agent Patent attorney Takehiko Suzue I03 (, OLn,

Claims (8)

[Claims] (1) In a method for treating a nonwoven fired metal web (1),
A method characterized in that such a web (1) is compressed isotropically. 2. A method according to claim 1, characterized in that the web (1) is cold isostatically compressed. 3. A method according to claim 1, characterized in that the isotropic compression is performed by a combination of a soft diaphragm (3) and a liquid (4). (4) The method according to claim 1 or 2, characterized in that the isotropic compression is performed by a combination of a felt-like material (5) and a compression plate (6). (5) A nonwoven fired metal web characterized by being isotropically compressed. (6) The nonwoven fired metal web of claim 4, wherein the web is adapted for use in a filter. 7. The nonwoven fired metal web of claim 4, wherein the web is adapted for use in a radiant surface combustion burner. (8) Change in transmittance, i.e. (P_m_a_x_.−P_m_i_n_.)/P_m
_a_x_. ×100 (where P_m_a_x_. is the maximum value of transmittance measured at any point on the web surface,
P_m_i_n_. 7. A nonwoven fired metal web according to claim 6, characterized in that the minimum value of transmittance measured at any point on the surface of the web (1) is less than 10%.